Sensing devices of the mentioned kind are used to guide agricultural machines, tractors, work devices or construction machines automatically along a structure that can be sensed, for example a plant row, a stand boundary or a soil furrow. The signal from the sensing device can serve in the automatic steering of a vehicle or of a self-driving machine and it can be used to control the working position of a farming implement horizontally or vertically.
A sensing device of the mentioned kind is known from DE 23 62 899 C2 whose sensing signal acts in the automatic lateral guidance of a self-driving agricultural harvesting machine. The sensing feelers are fixed to a support arm which projects forwards in the driving direction over the cutting mechanism of the harvesting machine such that they extend backwards in a flat circular arc. Close to the fixing location there are strain gauge circuits seated at the sensing feelers, which convert the deflection of the sensing feelers into an electrical signal. The mechanical bending stress of the sensing feelers elicited by the impacting harvested material is thus converted into an electrical signal for controlling the machine. This known design has the disadvantage that it is complex and susceptible to breakdown. The strain gauges are very sensitive and have to be protected in complex manner from the wrong mechanical stress, especially since they are arranged on the unfavorable impact side of the sensing feelers. The same applies to the connection lines which connect the gauges to the analysis circuit and have to be laid within a protective tube. Each time there is damage to the sensing feelers, an expensive element of the measuring system has to be replaced.
From DE 27 05 491 C2 a sensing device for automatic lateral guidance of a self-driving harvesting machine along a plant row is further known wherein a curved sensing feeler on the machine is mounted rotatably around an approximately vertical axis. The rotatable mounting is located within a divider tip of the machine closed with a casing and is equipped with an electrical measuring system which forms a control signal dependent on the angle of rotation of the hub element carrying the sensing feeler. This sensing device is also complex and its installation requires a protective casing.